Twlst-dkill



N. E. WOODS.

TWIST DRILL.

APPLICATION FILED SEPT. 30, 1919.

Patented July- 12, 1921.

2] MW: jvofllnanfif Woods,

UNITED STATES PATENT OFFICE.

Specification of Letters Patent.

TWIST-DRILL.

Patented July 12, 1921.

Application filed September 80, 1919. Serial No. 327,541.

To all whom it may concern Be it known that I NORMAN E. Woons, a citizen of the United tates, residing at Paterson, in the county of Passaic and State of New Jersey, have invented new and useful Improvements in Twist-Drills, of which the following is a specification.

This invention relates to improvements in drills of that class commonly known as twist drills.

Drills of this character, as at present constructed, are defective in that each cutting lip cuts a single heavy chip, which chips, in addition to throwing heavy strain upon the drill, tend to lodge in the flutes and cause friction and loss of power. The packing of these chips in the flutes also tends to obstruct the flow of the lubricant to the cutters, with a further increase of friction, loss of power, and generation of heat and the burning and deterioration of the metal of the drill at the point. Moreover, as the point has no cuttin action, but acts merely to center the dri l and force the metal beneath it from the center toward the cutting lips, the drill, as it feeds into the work. causes a compression of the metal from the center toward the periphery of the drill. This compression greatly increases the weight of a chip from its normal weight under a fixed feed per revolution until it is compressed to a number of times its normal thickness of cut per revolution. Such compression is more perceptible, and adds still greater resistance to the progress of the drill, when lubricant does not meet the point and the chip is softened in heating up by the friction of the cutting edge and the chisel point. Hence the drill is liable to break under the heavy strains and to become quickly dull, requiring frequent sharpening, and comparatively great power is required to feed the drill in its work. Drills provided with flutes extending to points at their heel edges also tend to further retard the clearance of the chips and cannot be uniformly tempered, owing to wide variations in the thickness of the metal at different portions thereof.

The general object of my invention is to provide a drill which overcomes the objections above noted to drills of ordinary construction, and which, therefore, is stronger and capable of resisting greater strains and is less liable to fracture than twist drills of the t pee in common use, and which will more e ciently lubricate the work and allow freer clearance of the chips and cut faster with less resistance than any ordinary type of drill. Further specific objects of the invention are to provide novel means in a drill structure for securing the desired results.

The invention consists of the features of construction, combination and arrangement of parts, hereinafter fully described and claimed, reference being had to the accompanying drawing, in which Figure l is a view in side elevation of a twist drill embodying my invention.

Fig. 2 is a plan view of the cutting end of the drill.

Fig. 3 is a cross-section through the drill and an object being bored thereby.

Fig. 4 is a diagrammatic lan view illustrating the cutting action 0 the lips.

Fig. 5 is a diagrammatic view in elevation of the same.

Fig. 6 is a view showing the divisions of the cuts and the chips formed by the cutting lips.

Referring to the drawing, 1 designates the body or shank of the drill. which is of the ordinary twist form, 2 and 3 the portions of the body forming the spiral cutting blades, 4 the central web connecting the inner edges of the blades, 5 and 6 the flutes formed by and between the twisted blades, 7 the chisel cutting point at the outer end of the web. and 8 and 9 the cutting lips at the outer edges of the blades 2 and 3.

In carrying my invention into practice, I provide the face of each cutter blade 2 and 3 with a longitudinally extending channel or groove. the face of the blade 2 being provided with a groove or channel 10 and the face of the blade 3 with a groove or channel 11. These grooves or channels referably extend throughout the length 0 the blades and intersect the cutting lips 8 and 9, thereby separating the respective cutting lips into a plurality of cutting portions. As shown, the groove 10 separates the lip 8 into alincd cutting portions 10 and 10 while the groove 11 separates the lip 9 into alined cutting portions 11 and 11".

It will be observed that the grooves 10 and 11 of the cutters are staggered with relation to each other, that is, arranged at different distances from the drill center, the lip 8 thus being separated by its groove 10 into a short straight inner cutting member 10" and relatively longer straight outer cutting member 10", while the lip 9, on the contrary,

a depth corresponding to the groove there-.

between. This is-clearly shown in Figs. 4, 5 and 6, wherein a, a and a 'respectively desi nate the chi sections and ridge formed by the cuttingllip 8 and Z), 6 and t the chip sections and ridge formed by the cutting lip 9. By the division of the chips in the manner stated the objections incident to ordinary drills, in which each lip forms a single vide chip, are avoided, in that the sectional chip may be cut with greater freedom and ease and with'a reduction of strain and friction, and the sections of the chip have greater ease of clearance, 1n thatthey will pass into and upwardly through the flutes in a tree and easy manner, and with out the tendency to bind therein and create great resistance and friction, as with chips of normal size. Accordingly, the working strains uponthe drill will be materially reduced and a drill ot a given size, and rotated at a given speed, may be operated to.

cut at greater speed than an ordinary drill and with less driving power. Furthermore, owing to the reduction of strain, the web i may be thinned or reduced in thickness by at least 15% less than the standard proportions, with the effect of narrowing the point.

7, and without weakening the drill, with the additional advantageous result of diminish ing to a great extent the compression'of the chips by the point of the drill, friction and undue heating of the drill point and chips being also thus reduced to a further degree.

one ofthe' cutters, is preferably made of In practice, the grooves 10 and ll of the cutters are preferably made deepest at the points where they intersect the lips 8 and 9 and then gradually diminish in depth to ward the drill shank, and the groove 10, of

less depth than the groove, as the groove 11, of the other cutter, with the result of further reducing the sizes (widths) of the chips made by one cutter with respect to those 7 made by the other, so that chips of different sizes will be formed which will more readily intermingle in their discharge to secure easy and rapid clearance. Another purpose of making the groove 11 deeper than the groove 10 is to allow greater clearance 0wlng to its greater distance from the drill center and 1ts greater ratio of cutting speed dueto the larger circle in which it travels, also, by such clearance, to prevent'burning' of the cutting edge at the outer wall of said groove 11 by high friction due to its speed.

This deeper groove 11 also further promotes tree supply of lubricant to the cutting surfaces. It will be understood that by the arrangement of the grooves 10 and 11 in staggered relation, or at different distances from the center point 7, provision is made so that a cutting portion oi each lip wlll remove the ridge left standing by the other nels 5 and 6 will be increased, insuring still further reduction of friction and any tendency of the chips to pack or bind therein. It will, of course, be understood that the grooves 10 and 11 also provide flow.chan nels for the passage of lubricant to the cut ting surfaces; The grooves may be forged during the process of manufacture or cast in the drill in the process of manufacturing a cast drill, or may be milled or otherwise formed in a drill whether prior to or after the working portion of the drill is twisted or made. I prefer to make the grooves initially of half round form or other suitable U-shape before the drill is twisted, as the result of such twisting action will be to impart to each groove the semi-elliptical or parabolically curved form shown. Such term of the groove, which is deepest toward the periphery of the drill and. shallowest at its side nearest'the center of the drill, results in the formation of a groove which allows freer clearance of the chips and also of the production of an overhanging cuttifig edge or point C at the intersection of the wider end of the groove with the lip, which edge serves to make a clean cut and prevent any drag and the formation of any fins or ragged surfaces on the chips liable to cause friction and retard the clearance of the chips.- Also said cutting edge tends to force the chips atright angles to thedirection of rotation, thus centering thcnrin the flutes and still further facilitating the clearance action. s c

It will be obvious that, in addition to the functional advantages stated, the grooves 10 and 11 also serve to form a pilot or leader for the drill, which guides the drill or causes it to run more accurately or centrally than a drillof ordinary type.

lVhile I have specified the use of a single groove in each drill lip, which is sufficient in drills up to a certain diameter, it is to be understood that any desired or required number of grooves may be formed in each drill lip as may be found most advantageous in drills of different diameters. Also while I have shown and described the-use llll of grooves of certain form in the drill lips, I do not wish to be strictly confined thereto, except when specifically set forth in certain claims, as while such form of grooves have been found to be of desirable and special advantage, especially in their use in large drills which cut coarse chips, grooves of other equivalent form, when employed in connection with the other stated improvements of my invention, may be used in drills olfsmall size which cut comparatively small c ips.

In twist drills of ordinary construction the heel edges of the cutting members 2 and 3 generally extend to points or flukes, with the result that the flutes 5 and 6 are contracted thereby and the cutting members made of such irregular form and varying widths as to make it impossible to temper the drill evenly or in such manner to be free from flaws. I overcome this objection by rounding the heel ends of the cutting members, as indicated at 12, thus widening the flutes 5 and 6 and removing an excess of metal adding to the difficulty in tempering the drill evenly. By this construction an added advanta e is obtained, in that in the upward flow o the masses of chips through the flutes pockets or channels 12' are produced between the same and the surfaces 12, affording additional channels for the flow of lubricant to the cutting surfaces.

Having thus fully described my invention, I claim 1-- 1. A twist drill having cutting members provided with cutting lips and with grooves in their faces intersecting said lips, the heel portions of said members being rounded off to form an oil channel between the same and the discharging mass of chips.

2. A twist drill having cutting blades provided with cutting lips, each divided by a groove into a plurality of longitudinally alined cutting edges of varying length one with respect to the other, each groove being of semielliptical form and deepest at its side farthest from the longitudinal center of the drill and shallowest at its side nearest the center of the drill, the outer edge wall of the groove overhan 'ng and forming at its point of juncture with the outer cutting edge a cutting point.

3. A twist drill having its cutting blades provided with cutting lips, each divided by a groove into a plurality of cutting edges, each groove being of a form produced by the resulting change of shape from a primary U-shape in the blank from which the drill is made during the twistin of the blade forming portion of the drill blank into spiral shape.

4. A twist drill of the present used type having two major cutting members provided with two straight major cutting lips or edges. so arranged in relation to each other as to be practically radial from the center of the axis of the drill body leaving a very small chisel point or web at the center, and with grooves in their faces inter secting said straight major cutting lips or edges forming minor straight cutting lips, the heel portions of said members being rounded off t6 reduce the excess body of metal so that the solution used in drilling will keep the thinner members cooler, than if same was of the usual shape and thickness, also to allow more drilling solution to enter the hole while drilling.

5. A twist drill of the present used type having two major cutting members provided with two major straight cutting lips or edges, so arranged with relation to each other as to be practically radial from the center of the axis of the drill body, thus uniformly thinning out the web between the cutting members by at least 15% less than the standard proportions and leaving a very small chisel point at the center, said cutting members having main grooves or flutes and auxiliary grooves in their faces intersecting said major cutting lips or edges and forming minor straight cutting lips, the thinning of said Web correspondingly increas ing the depth of the said main grooves or flutes.

6. A twist drill having cutting lips, each of which is separated by an intersecting groove into cutting portions of diiferent widths, the separating grooves of the respective lips being arranged at different distances from the drill point, the more distant one of said grooves being deeper than the other.

7. A twist drill having cutting lips, each divided by a groove at a different distance from the axis of the drill into a plurality of cutting portions, each groove being of semi-elliptical form. the more distant one of said grooves being deeper than the other.

In testimony whereof I affix my signature.

NORMAN E. WOODS. 

